The invention relates to systems and methods for mapping and ablating the interior regions of the heart for treatment of cardiac conditions.
Physicians make use of catheters today in medical procedures to gain access into interior regions of the body to ablate targeted tissue areas. It is important for the physician to be able to precisely locate the catheter and control its emission of energy within the body during tissue ablation procedures.
The need for precise control over the catheter is especially critical during procedures that ablate endocardial tissue within the heart. These procedures, called electrophysiological therapy, are use to treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician then further manipulates a steering mechanism to place the electrode carried on the distal tip of the catheter into direct contact with the endocardial tissue that is to be ablated. The physician directs energy from the electrode through tissue either to an indifferent electrode (in a unipolar electrode arrangement) or to an adjacent electrode (in a bi-polar electrode arrangement) to ablate the tissue and form a lesion.
Physicians examine the propagation of electrical impulses in heart tissue to locate aberrant conductive pathways and to identify foci, which are ablated. The techniques used to analyze these pathways and locate foci are commonly called xe2x80x9cmapping.xe2x80x9d
Conventional cardiac tissue mapping techniques use multiple electrodes positioned in contact with epicardial heart tissue to obtain multiple electrograms. These conventional mapping techniques require invasive open heart surgical techniques to position the electrodes on the epicardial surface of the heart.
An alternative technique of introducing multiple electrode arrays into the heart through vein or arterial accesses to map endocardial tissue is known. Compared to conventional, open heart mapping techniques, endocardial mapping techniques, being comparatively non-invasive, hold great promise. Still, widespread practice of endocardial mapping techniques has been hindered by the difficulties of making suitable endocardial electrode support structures, including severe size constraints, strength and durability demands, and the sheer complexities of fabrication.
An endocardial mapping structure can potentially remain in place within a heart chamber for several thousand heart beats. During this time, the powerful contractions of heart muscle constantly flex and stress the structure. The structure must be strong and flexible enough to keep the electrodes spaced apart both longitudinally and circumferentially without failure and without shed parts. In addition, there is also the need to provide simple, yet reliable ways of electrically coupling multiple electrodes to external sensing equipment. Still, though strong and durable, the structures must cause no trauma when in contact with tissue.
While prior multiple electrode support structures may attempt to provided the requisite strength and flexibility, they have created envelopes with blunt, non-conforming contours that can poke into tissue and cause trauma during heart contractions.
It can be seen that providing economical, durable, and safe multiple electrodes in a package small enough to be deployed within the heart often poses conflicting challenges.
This invention has as its principal objective the realization of safe and efficacious endocardial mapping techniques.
The invention provides structures for supporting multiple electrode arrays within the heart that address the conflicting challenges. They minimize structural stresses and failures while avoiding tissue trauma. At the same time, they possess minimal structural parts and complexity, lending themselves to practical, economical fabrication techniques.
In providing these and other benefits, the invention provides an electrode support structure comprising a hub having an axis and a slot that extends across the axis through the hub. The structure also includes a generally flexible integral body with a mid-section and opposed pair of spline elements extending from the mid-section. The spline elements have terminal ends spaced from the mid-section.
According to the invention, at least one spline element is insertable terminal end first through the slot. The mid-section engages the slot upon entering it. This engagement secures the integral body within the slot, with the opposed pair of spline elements radiating free of the slot for carrying one or more electrodes.
In a preferred embodiment, a base is connected to the terminal ends of the spline elements. The integral body is flexed between the hub and the base into a predetermined three dimensional shape.
A preferred embodiment includes at least two integral bodies and a matching number of slots on the hub. The slots are spaced both circumferentially and axially on the hub to hold the spline elements in the desired angular and circumferentially spaced three dimensional pattern.
Support structures that embody the features of the invention permit the reliable assembly of multiple spline elements into a predetermined, efficacious pattern. The structures control and maintain precise angular and longitudinal orientation of the spline elements about the hub members during use. The structures also support the spline elements to prevent sharp bends and failure-causing stresses at critical junctions in the structure.
In a preferred embodiment, the slotted hub provides a geometry in which the mid-section of the integral body extends generally perpendicularly from the axis of the hub member. The flexing of the spline elements between the hub and base creates an essentially spheroid structure whose curvature approximates the curvature of the endocardium. The structure presents a curved, uniform distal surface that follows the natural contour of endocardial tissue.
In a preferred embodiment, the slot hub does not project appreciably beyond the envelope of the structure. The hub lies essentially within the plane of the distal surface to present a surface essentially free of major projections that can extend into and damage endocardial tissue. Blunt tissue trauma is avoided. This geometry also makes it possible to place electrodes carried near the hub into intimate contact with endocardial tissue.
Another aspect of the invention also provides a catheter comprising a guide tube having a distal end that carries an electrode support structure as just described. In a preferred embodiment, the catheter includes a sleeve slidable along the guide tube in one direction upon the electrode support structure to collapse it for introduction into the body. The sleeve slides along the guide tube in another direction to move it away from the electrode support structure, deploying it for use within the body.